The present invention relates generally to inkjet printheads, and more particularly to controlling nozzle firing order in inkjet printheads.
A conventional inkjet printing system includes a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
Typically, the printhead ejects the ink drops through the nozzles by rapidly heating a small volume of ink located in vaporization chambers with small electric heaters, such as thin film resisters. Heating the ink causes the ink to vaporize and be ejected from the nozzles. Typically, for one dot of ink, a remote printhead controller typically located as part of the processing electronics of a printer, controls activation of an electrical current from a power supply external to the printhead. The electrical current is passed through a selected thin film resister to heat the ink in a corresponding selected vaporization chamber.
In one type of printhead, switching devices, such as field effect transistors (FETs), are coupled to each thin film resistor to control the application of the electrical current through the selected thin film resistors. In one printhead arrangement, the resistors are grouped together into primitives, with a single power lead providing power to the source or drain of each corresponding FET for each resistor in a primitive. Each FET in a primitive has a separately energizable address lead coupled to its gate, with each address lead shared by multiple primitives. In a typical printing operation, the address leads are controlled so that only a single resistor in a primitive is activated at a given time.
In one arrangement, the address lead coupled to the gate of each FET is controlled by a combination of nozzle data, nozzle addresses, and a fire pulse. The nozzle data is typically provided by the electronic controller of the printer and represents the actual data to be printed. The fire pulse controls the timing of the activation of the electrical current through the selected resistor. Typical conventional inkjet printing systems employ the electronic controller to control the timing related to the fire pulse. The nozzle address is cycled through all nozzle addresses to control the nozzle firing order so that all nozzles can be fired, but only a single nozzle in a primitive is fired at a given time.
One type of printhead includes an address generator and a hard-coded address decoder at each nozzle for controlling nozzle firing order. In this type of printhead, the nozzle firing sequence can only be modified by changing appropriate metal layers on the printhead die. Thus, if a new nozzle firing order is desired in this type of printhead, the set nozzle firing sequence is modified by changing one or more masks to thereby change the metal layers that determine the nozzle firing sequence.
For reasons stated above and for other reasons presented in greater detail in the Description of the Preferred Embodiments section of the present specification, an inkjet printhead is desired which has a programmable nozzle firing order.
One aspect of the present invention provides a printhead including a group of nozzles and a group of firing resisters corresponding to the group of nozzles. The printhead includes a programmable nozzle firing order controller configured to provide address generator control signals. The printhead includes a nozzle address generator configured to respond to the address generator control signals to provide a nozzle address. The nozzle address controls a sequence of which firing resister has electrical current pass through it at a given time to thereby control a firing order of the nozzles.
In one embodiment, the programmable nozzle firing order controller includes a right scan starting address register holding a right scan starting address value representing a starting value for the nozzle address generator for printing in a right scan direction. In one embodiment, the programmable nozzle firing order controller also includes a left scan starting address register holding a left scan starting address value representing a starting value for the nozzle address generator for printing in a left scan direction. In one embodiment, the scan left and scan right starting addresses are stored in a shared starting address register, which is re-written with each change of scanning direction.
In one embodiment, the programmable nozzle firing order controller includes a control register holding control bits to control the nozzle firing order sequence provided by the nozzle address generator after a given scan right or left starting address. In one embodiment, the control register has a direction field representing a direction value to indicate to the address generator a scan direction of the inkjet printhead. The nozzle address generator responds to the direction value to either count up or count down based on the direction value. In one embodiment, the control register has an address sequence field representing an address sequence value to control a sequence in which the nozzle address generator counts up or down from a given scan right or left starting address.
In one embodiment, the inkjet printhead includes an internal address bus configured to be coupled to a serial bus for communicating with an electronic controller in an inkjet printing system and an internal data bus configured to be coupled to the serial bus for communicating with the electronic controller. The programmable nozzle firing order controller includes registers coupled to the internal address bus and the internal data bus. In one embodiment, the data and addresses are shared on one internal bus to save printhead die area, and signals indicate whether data or addresses are on the shared bus at a given time.
In one embodiment, the inkjet printhead includes at least a second group of nozzles and at least a second group of firing resisters. Each group of nozzles and corresponding group of firing resisters are grouped in a corresponding primitive. In one embodiment, each primitive includes a group of switches. Each switch in the group is coupled to a corresponding firing resister in the group of firing resisters and is configured to switch the electrical current through the firing resister to thereby fire the corresponding nozzle.
In one embodiment, the switches each include a field effect transistor (FET) having a gate controlled by the nozzle address. In one embodiment, the gate of each FET is also controlled by nozzle data. In one embodiment, the gate of each FET is also controlled by a fire pulse for controlling the timing of the activation of electrical current through the corresponding firing resister. In one embodiment, all FETs in a primitive are coupled between a primitive power and a primitive ground.
One aspect of the present invention provides a printhead assembly having at least one printhead. Each printhead includes a group of nozzles and a group of firing resisters corresponding to the group of nozzles. Each printhead includes a programmable nozzle firing order controller configured to provide address generator control signals. Each printhead includes a nozzle address generator configured to respond to the address generator control signals to provide a nozzle address. The nozzle address controls a sequence of which firing resister has electrical current pass through it at a given time to thereby control a firing order of the nozzles.
One embodiment of the inkjet printhead assembly includes multiple printheads.
One aspect of the present invention provides an inkjet printing system including an electronic controller configured to provide data and at least one printhead. Each printhead is configured to receive the data from the electronic controller. Each printhead includes a group of nozzles and a group of firing resisters corresponding to the group of nozzles. Each printhead includes a nozzle firing order controller configured to provide address generator control signals. The nozzle firing order controller is programmable with the data from the electronic controller. Each printhead includes a nozzle address generator configured to respond to the address generator control signals to provide a nozzle address. The nozzle address controls a sequence of which firing resister has electrical current pass through it at a given time to thereby control a firing order of the nozzles.
One embodiment of the inkjet printing system includes a serial bus for communicating data between the electronic controller and each printhead. In one embodiment, each printhead includes an internal address bus configured to be coupled to the serial bus and an internal data bus configured to be coupled to the serial bus. The programmable nozzle firing order controller includes registers coupled to the internal address bus and the internal data bus. In one embodiment, the data and addresses are shared on one internal bus.
One aspect of the present invention provides a method of generating a nozzle address in a printhead. The method includes providing address generator control signals from a programmable nozzle firing order controller in a printhead. The method includes generating a nozzle address in response to the address generator control signals. The method includes controlling, with the nozzle address, a sequence of which firing resister of a group of firing resisters has electrical current pass through it at a given time to thereby control a firing order of a group of nozzles corresponding to the group of resisters.
In one embodiment, the method includes holding, in the programmable nozzle firing order controller, a right scan starting address value representing a starting value for generating the nozzle address for printing in a right scan direction. In this embodiment, the method also includes holding, in the programmable nozzle firing order controller, a left scan starting address value representing a starting value for generating the nozzle address for printing in a left scan direction.
In one embodiment, the method includes holding, in the programmable nozzle firing order controller, control bits to control the nozzle firing order sequence provided by the nozzle address after a given scan right or left starting address. In one embodiment, the method includes holding, in the programmable nozzle firing order controller, a direction field representing a direction value to indicate a scan direction of the inkjet printhead. In one embodiment, the method includes counting up or counting down based on the direction value. In one embodiment, the method includes holding, in the programmable nozzle firing order controller, an address sequence field representing an address sequence value to control a sequence in which the nozzle address is generated from a given scan right or left starting address.
In one embodiment, the method includes programming registers in the programmable nozzle firing order controller to change the sequence of which firing resister of the group of firing resisters has electrical current pass through it at a given time to thereby program the firing order of the group of nozzles corresponding to the group of resisters.
The inkjet printhead according to the present invention includes the programmable nozzle firing order controller which can be programmed to change the nozzle firing order in the printhead. As a result, new masks do not need to be generated if a new firing order is desired. The programmable nozzle firing order permitted by the programmable nozzle firing order controller allows architects of inkjet printhead designs more freedom to experiment with different firing orders without the necessity of generating new masks and allows a single printhead die design to be employed across a wide variety of inkjet printing system products, which would otherwise require custom printhead die due to varying fire order requirements.